Monday, October 23, 2017

Oh, patents! Melitta® Paper filters

Copyright © Françoise Herrmann
The crimped and cut design retained for Melitta® paper filters, to this day, was originally recited nearly 100 years ago. 

As recited in GB451197, granted on July 31, 1936, to Horst Wolfgang Bentz (Melitta’s son), the Melitta® paper filter resolved several problems of the prior art. In particular, the way in which prior art paper filters decreased the rate of filtering because when pressed into the ribbed filtering cup, the paper doubled or tripled in thickness on the walls of the ribbed cup. In turn, the excess paper, thus used, also increased waste and costs. Additionally, prior art paper also tended to tear when the filtering cup was wet.
To resolve this problematic situation, the invention recites a paper filter, already shaped into a cup, prior to use, even if it may be folded for packaging purposes. The walls of the paper filter are cut and crimped together into a cone-shaped vessel. (recited alternatively as glued, goffered, stitched or stamped), In one embodiment of the invention, a variation of which is retained to date, the apex of the cone-shaped filter is either folded back on the side (fig. 5), or cut and crimped (fig. 3), like the edges of the filter walls. In another (un-retained) embodiment of the invention (fig. 6), the bottom of the filter is separately cut and attached by means of crimping (goffering, stamping, gluing, etc.)

The abstract for this invention is included below with the sheet of patent drawings, illustrating the new 1936 Mellita® paper filters, their new seams, and options for cutting, and folding back, or crimping, the apex of the cone, or for attaching a separate bottom altogether. The image of a commercially available, cut and crimped, 2017  box of size 4 Melitta® paper filters is also included above.   
Filter paper for use in a grooved or ribbed cup or like vessel, for example for making infusions of tea or coffee, is preformed according to the shape of the vessel from one or more blanks by folding and then uniting the edges by crimping, stitching or adhesive. Fig. 2 shows a paper element formed from a single blank with edges d crimped together. A separate blank may be used to form the bottom, its periphery being turned upward and united to the blank forming the side wall by crimping. The element shown in Fig. 5, has its lower portion strengthened by additional thicknesses g. It is cone-shaped with the apex turned up and attached to the side wall by crimping, so that it is kept in this position. [Abstract GB45197]


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